METEOROLOGY



NAME _________________________________________ DATE ___________________

Activity 4A:

TEMPERATURE AND TEMPERATURE ADVECTION

NOTICE: This activity consists of two parts:

1. This packet (complete first)

2. Internet files obtained from Mr. Nap’s meteorology course page

(staple internet files to this packet)



Educational Outcomes:

The Earth-atmosphere system is heated unevenly by solar radiation. Low latitudes receive more energy from the sun than they lose to space as outgoing infrared radiation. High latitudes experience more outgoing than incoming radiation. These energy excesses and deficits are balanced by horizontal movements (called advection) of heat energy poleward by migrating air masses, storm circulations, and ocean currents. The horizontal transport of air from a region of relatively high temperatures to a region of relatively low temperatures by wind motion is referred to as warm air advection. Conversely, the transport of air from a region of relatively low temperatures to a region of relatively high temperatures by wind motion is called cold air advection. Although on a global and annual average basis, there is a net poleward flow of heat in midlatitudes, on any given day, some areas may experience warm temperature advection while other areas experience cold temperature advection. Identification of areas of warm and cold temperature advection requires analysis of the air temperature pattern that is represented by isotherms.

After completing this activity, you should be able to:

□ Draw lines of equal temperature (isotherms) to show the pattern of air temperatures across the nation at map time.

□ Locate regions on a weather map where cold and warm air advections are likely to be occurring.

□ Relate temperature advection patterns to circulations of weather systems.

Materials: Hard copies of the Activity File plus designated Image(s).

Investigations:

1. Temperature patterns are found on weather maps by drawing lines representing certain temperatures. These lines are called isotherms because every point on the same line has the same temperature value. Each isotherm separates temperatures having values higher than the isotherm from temperatures having lower values.

The following map shows temperatures in OF at various weather stations. Assume each number centers on the location it represents. The 60 OF isotherm has been drawn and labeled. Complete the 70 OF isotherm shown. Also, draw the 80 OF isotherm. Be sure to label each isotherm at both ends.

60 70

58 71

63

84

60

65

81 83

76

84 84 87

2. Isotherms are drawn at regular intervals on this map. The interval between successive

isotherms is ______________ Fahrenheit degrees.

Tips on Drawing Isotherms:

a. Always draw an isotherm so that temperatures higher than its value are consistently to one side and lower temperatures are to the other side.

b. Assume a steady temperature change between neighboring stations when positioning isotherms; that is, use interpolation to place isotherms.

c. Adjacent isotherms tend to look alike. The isotherm you are drawing will often parallel in a general way the curves of its neighbor because changes in air temperature from place to place are usually (but not always) gradual.

d. Continue drawing an isotherm until it reaches the boundary of plotted data or "closes" within the data field by making its way to its other end and completing a loop.

e. Isotherms can never be open ended within a data field and they never fork or touch or cross one another.

f. Isotherms cannot be skipped if their values fall within the range of temperatures reported on the map. Isotherms must always appear in sequence for example, when the isothermal interval is 10 degrees, there must be a 50 OF isotherm between the 40OF and the 60OF isotherms.

g. Always label isotherms.

3. The regional weather map on page 5 shows wind observations taken at several weather stations. Three representative isotherms have been placed on the

map. The isotherm values are ________ OF, _______ OF, and ________ OF. Hence,

the interval between isotherms is ________ Fahrenheit degrees.

4. Warm air advection occurs where the winds blow across the isotherms from the higher (warmer) values to the lower (colder) values. That is, warmer air is being transported to the station by the horizontal winds. Based on this factor alone, one would expect temperatures to rise in the near future. Cold air advection occurs where winds blow across the isotherms from the lower (colder) values to the higher (warmer) values. Then, colder air is being transported to the station by horizontal winds.

Based on wind directions and the isotherm pattern on the map, determine the type of air advection that would be occurring at each station and circle warm or cold.

Station Advection type

A warm cold

B warm cold

C warm cold

D warm cold

5. In general, from the wind patterns associated with weather systems, areas southeast of Lows can be expected to have (warm) (cold) advection, while areas to the west have (warm) (cold) air advection.

6. Areas to the east of Highs would have (warm) (cold) air advection, while not shown here, areas to the west of Highs should have (warm) (cold) air advection.

On actual weather maps, the patterns of isotherms and winds vary greatly. The intensity of temperature advection will depend on the wind speeds, the angle at which the wind crosses the isotherms, and the closeness of neighboring isotherms. In general, the faster the wind, the more perpendicular the angle, and the closer the isotherm lines, the stronger the advection.

Not surprisingly, one can expect (warm) (cold) air advection behind cold fronts and (warm)(cold) air advection behind warm fronts.

7. Where the horizontal winds blow parallel to the pattern of isotherms, we would expect (warm) (cold) (no) temperature advection.

8. Recall that air temperatures are governed by a combination of temperature advection and radiational controls. With no temperature advection, the lowest temperature of the day is likely to occur around (sunrise) (sunset). If a day's lowest temperature occurs just before midnight, then (warm) (cold) air advection likely occurred during the afternoon and evening hours.

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